Subscriber television system



R. o. GRAY ET Al.

SUBSCEIBER TELEVISION SYSTEM Oct. 20, 1953 2 Sheets-Sheet 1 Filed July 2, 1948 N -mi Oct. 20, 1953 R, C)I GRAY ET AL 2,656,406

` SUBSCRIBER TELEVISION SYSTEM Filed July 2, 1948 2 Sheets-Sheet 2 30 Bev /sl /32 E S/ V TUNER a vIDI-:o '/53 VDEO DETECTOR AMPLIFIER X sYNcH. VERT; SIGNAL SWEEP sEPARAToR DR'VE x35 fas i /51 PULSE HORIZ.

PHASE SWEEP MODULATOR DRIVE wire line conducor To 1ronsmi1'ler.

43 FILTE R FOR , CODING 5|G. /4/39 42 AUDIO TUNER AUDIO AND AMPLIFIER DETECTOR RIcI-IARD O. GRAY ERwIN M. Ro cHKE 1N ENToRs Patented Oct. 20, 1953 UNITED STM-fas 656,496 PATENT GFF .SUBSCBJBEB lllliLlVISION VSYSTEM Richard 0. Gra-y and Erwin M. Roschk e, Broadview, I'll., .assignors to Zenith Radio Corporation, a. .corporation of Illinoisy Application July 2, 1948, Serial No. 36,778

(Cl. P18-5.1)

17Clalms. 1

This invention relates to radio signalling vs ystenis, and more particularly tc Such systeme of the Subscriber type.

It is an object of this invention to provide such a system in which a coding signal is utilized for coding a transmitted signal, and in which the characteristics o; the coding signal are changed from .tiine to time.

It is .a further object of this invention to Provide .such .esvetern wherein Ykey Sighele .are trenemitted 4to Subscriber receiver systems to indicate the .times of occurrence .of .Such changes in cherecterisitcs in .the .above coding signal- Yet another obieot .of this invention is to provide such a .system wherein .euch key eisneis .are transmitted to subscriber receiver systems by means lof some private link, .such as e telephone une, power .line and like, between 'transmitter and receiver.

A .Still further object of this invention .is to provide -euch e system. Vin which Vthe above .nienticned coding signal .is transmitted concernitantly with the transmitted coded signals 'but with unaltered characteristics, to be .utilized yin sbscriber receiving .Systems ,for decoding the coded signalet A more particular oniect .of .this .invention is to provide e television system' .in which .e .coding signal is utilized for Ycoding a vtranslnitted television signal, and wherein the .coding signal is transmitted to subscriber receiver systems dulated preferably `on the audio carrier portion of the television signal.

It is ,an additional ohl'ect .of .this ...invention to provide asubserption television system wherein a. characteristic of one encoding .Signal .is varied to'develop a second .encoding .signal and wherein either one of .these encoding' .Signals may be used for encoding purposes.

It is still another object of this invention .to

provide a subscription television.reeeivel :for nti.- lizinga television signal coded in accordance with a certain coding schedule in which one decoding signal is operated on -by a secondV decoding signal to develop la third decoding signal which represents the coding schedule of thetelevlsion signal,-

`Yet another particular. object of this invention is Ito .provide means in ,such a television system for changing the characteristics of the coding signal .from time -to time, and for .transmitting key .signals to indicate :the times cof Ioccurrence of such changes, .these key .signals .being trans.- mitted =to subscriber `receiver y.systems by may :of power lines, phone flines, or .thelike A furtheriobject of this invention is to vprovvide in such coded electrical signalling systems, V.a receiver system to receive and decode signals-transmitted in the above `mentioned manner, upon rece'lpt of the coding signal and the 'key signals.

it is still a further object of this invention to provide asubscription television receiver wherein mode changes are effected at a rate faster than the recurrence 4nite of the Scanning neide.-

The feetnree .of .this invention, which ore loeiieved to be new, are Set forth with yn eirtion.larit.Y in the appended claims. The invention itself. DQWEVEI, .Qgiihdi With further .Objects .and .dii- Veintn'ds thereof mit? 'Qi-Sli be llllieISliOd Dy???- erence to the following .description when .te en in conjunction with the accompanying drawings, in which:

'Figure i Shows e television transmitter system incorporating the invention, and

Figure 2 shows a receiver system operating in conjunction with the transmitter of Figaro The venous components that constitute the Systems of `Figure 1 .and Figure 2 .ere .in them.- selves either quite conventional, or have been Previously described in .depending iannlziceiti-on Serien No.. '142.374, entitled RedioWire .Signal- 1mg system. nnen ka ai.. nennen- 1 18 .19.47. .or in copending application erial ANo. 773,848, elititled jlmage Transmission System, Bioschka filed September 1 3, 19.47. 139th these applications ars assigned tothe present assignee, and have now issued respectively as Patent 2,510,046 on Mey 30. 19.50. .end .es Potent 2547.598011 April I3, 1951, These componentsl are therefore Shown in .block form, and a .detailed .description thereof is believed to be unnecessary.

Referring now to Figure q1, the television transmitter shown herein includes `a usual camera 'I. Camera l comprises a conventional .lens system 2 for focusing images upon the screen of television nick-up tube .3. niek-nntnbe .3 :being of the iconoecope or image ...orthicon type, and ineluding a horizontal scanning coil 4 Yand 'vertical scanning coil `5. 'Video signals from tube 8 are amplied in video amplifier st-ages, and synchronizing signals and 'krlarlking pedestals .are mixed with ythese video Signals in synchronizing Signal and pedestal mixer Stage-1. Sieneie frein stage 1 are impressed on background reinsertion device 8 and the resulting .program signals, appropriately adjusted as to background mlevel, are modulated on the video carrier in carrier Wave generator and modulator stage 3, and thence radiatedfrom antenna I0. Vertical and uhorizorrta-1 synchronizing signal-ls are generated in vertical and horizontajisynchronizing signal generators H, and these signals are applied to ,stage j `by way of leads lI2 and |53 respectively. Vertical synchronizing signals from stage LI lare further impressed on vertical sweep generator 14, the output of which is coupled to the vertical scanning coil 5 of tube 3. Similarly, horizontal synchronizing signals -from stage Ijl are y,further impressed on horizontal sweep generator 4I 5 through a conventional pulse phase modulator i6. jReference -is made to page 473 of Wave Forms," MIT Radiation Lab Series, volurne l1,9, McGraw- Hill, 31949 ,for a detailed description of .one type of Pulse nheee modulator .editable .for :inclusion in the present system. 'The modulator I6 is 3 controlled, in a manner to be described, to alter the horizontal sweep of pick-up tube 3, the output of sweep generator I being applied to the horizontal sweep coil 4 of this tube. That is, assuming that a sine-wave signal is applied to modulat'r 5|6, the pulses applied to sweep generator I5 are timeor phase-modulated in accordance with this sine wave. This causes the timing of the horizontal sweep of tube 3 to vary in a continuous, cyclical fashion relative to the horizontal synchronizing signals developed by generator II. Therefore, the timing of the video signals generated by tube 3 varies in similar fashion relative to the horizontal synchronizing signals applied to mixer 'I from generator I I. In this manner the aforementioned program signals are effectively coded since the video signal portion thereof does not have a fixed time relation with respect to the horizontal synchronizing signal portion, but has a timing that varies in accordance with the sine wave applied to pulse-phase modulator I6. Although modulator I6 is shown as being included in the horizontal sweep circuit, such a modulator may similarly be included in the vertical sweep circuit, as will become apparent as the present description proceeds.

Vertical synchronizing pulses from generator I| are further impressed on random frequency divider I1, and random frequency divided pulses from divider I1 are utilized to trigger key signal generator I8l a burst of key signal being obtained on leads I9 in response to each of these random frequency divided pulses. The key signal generator may be of the type disclosed in aforementioned Patent 2,547,598 and described in detail therein in conjunction with Figure 12. Frequency divider I1 need not necessarily be of the random type, and may be any known frequency divider circuit. For example, the frequency divider may be of the type disclosed in aforementionedv Patent 2,547,598 and fully discussed therein with reference to Figure 11. However, when it is desired that the frequency division of the pulses in divider II be of a random nature, the circuit of this divider may have a form similar to that disclosed in copending application Serial No. 32,457, entitled, Random Frequency Divider, Erwin M. Roschke, filed June l1, 1948, issued March 1l, 1952, as Patent 2,583,413, and assigned to the present assignee.

Leads I9 connect the transmitter with subscriber receiving systems, and these leads may conveniently'be some form of Wire line conductor such as power lines, phone lines, and the like, or these leads may be a coaxial cable, or when so desired, the key signals may be radiated on suitable carriers to the subscriber receivers. The frequency of the key signals is usually made such that is does not interfere with signals normally carried by the leads I9, however, the key signals may be transmitted to subscriber receivers in any suitable form such as pulses, or the like, the sole function of these key signals being to indicate to subscriber receivers the times when certain changes occur in the coding of the transmitted signal.

The pulse phase modulator I6 is controlled by coding signal generator 2U, signals from generator 20 being impressed on this modulator through phase inverter and switch 2|. Signal generator 2|) may take the form of any wellknown type of vacuum-tube oscillator, and unit 2| may be of the type disclosed in aforementioned Patent 2,510,046 and described in detail therein in conjunction with Figure 6. Phase absence 1 inverter and switch 2| is utilized to `change the characteristics of the coding signal impressed on modulator I6, which changes occur at various time intervals. In the illustrated embodiment, stage 2| acts to invert the phase of this coding signal in response to actuation of key frequency filter and switch operator 22. Stage 22 has previously been described in detail in aforementioned Patent 2,547,598 in conjunction with Figure v14 thereof. Bursts of key signal from leads I9 are impressed on stage 22 by way of leads 23, and in response to each burst of key signal, the next succeeding vertical synchronizing pulse on leads 24 connecting generator I.| to stage 22, acts to cause stage 2| to invert the phase of signals passing therethrough, and upon the termination of each burst of key signal, the next succeeding vertical synchronizing pulse on leads 24 acts to reverse this action.

Signals from generator 20 may take on any desired form such as pulses, saw tooth waves, sine waves, and the like and to add to the coding characteristics of these coding signals, they may be phase or frequency modulated by any suitable means, when so desired. The signals from generator 2D preferably are modulated on the audio carrier in carrier wave generator and modulator stage 25, this modulation being effected in any desired fashion, and these signals being impressed on stage 25 by way of leads 26. The audio signals accompanying the above described video signals are impressed on audio amplifier stage 21 from a usual microphone or translating device 28, the amplified audio signals are modulated on the audio carrier in stage 25 together with the coding signal, and the modulated audio carrier is radiated by antenna 29.

Hence, it can be seen that the transmitted television signal is coded by means of a coding signal from generator 20, which coding signal is transmitted on the audio carrier. It can further be seen that the coding signal as applied to modulator I6 is phase inverted from time to time, the

times of such phase inversion being indicated to subscriber receiver systems by the key signals over private link I 3, so that corrective circuits may be actuated thereby in these receivers. It is apparent that stage 2| need not necessarily be 'l a phase inverter stage, as any suitable change may be .imparted to the characteristics of the cod1ng signal, so long as a similar corrective change is effected at the subscriber receiver at proper intervals.

Such a subscriber receiver is shown in Figure 2. Referring now to Figure 2, video signals are received on antenna 30, these signals being tuned and detected in tuner and detector stages 3|. A detected video signal from stage 3| is amplied in video amplifier stage 32, and amplified signals from stage 32 are impressed on receiver image tube 33 in the usual manner. Synchronizing signals are removed from the detected. signal by means of synchronizing signal separator stage 34, and vertical synchronizing signals sweep coil 36 of tube 33. nizing signals from separator 34 are applied to derived from this stage are applied to vertical sweep drive 35 to actuate this drive, drive 35 in turn providing scanning potentials to vertical Horizontal synchrohorizontal sweep drive 31 through pulse phase modulator 38, which modulator is similar to modulator I6 of Figure 1. The output of horizontal sweep drive 3l is impressed on horizontal sweep coil 38' of tube 33.

Audio signals accompanying the previouslyde..

s"scribed video signals 'fare lecci-'ved -rantenna $9, and isuchsignals lare tunedsand detectedin tunerl and Ydetector -stage 46. vtuned #and .1dei- 'tected si'gnal `.is .amplified audio amplifier #L and 1reproduced inisignal ltranslating@device 42. 1

The previouslydescribedeoding signalen-removed from the audio carrier byfiilterfstagefii,#andthis coding's-ignal fis impressed onipu'lse "modulator 38 th-rough. :phase inverterfandswitchl,.thisxphase Yinverter -and .switch similar sto. switch y:2i fi-Figure l.

In fthe -1absense-of Kflrey signalson 1conductors 49 :phase inverter I'and Switchs :passes thief-coding {signa-1 -from filter "L43 tc .modulator Y38 ein faa..1nc rir- Iinverted -manner, `and @the horizontal #sweep fof 1' i 44.0 invertythgphase ofi-.the received' coding-1sig vvnali-as appliedtovmodulatorfein correspondence te such-inversion at'the"transmitterssoithatztuhe @33 -continues --to reprockice .the :received video 1signal.

Whilefawparticular fembodiment foffthe inven- 4Ation? Yhasy been shown' andfflescribemmodication maybe-made=wit lfioutfdepating therefrom. The

modifications i'f-as` fall rwithinftlue vtr-ue'ispirit Tand Y scope'of 'the invention.

We claix'n:

1. A subscription receiver fora-'itilizing electrie caL-SignaIs coded infiaccordance with 'sa l2certain coding schedulev determined'fbyva yfcharacterisi'ic of l a -codingssignal for which-'saidcharacteristic is4 i altered `during fspaced time interim-ls,'4 andi 1to1' yutilizingafdecodingsignal havingacharacteri'stic .correspondingto said fciiaracteristicfof Is'airdicod-e -ing signaliand received-iconcurrently miith. aid electrical signalsf andfforfr alsoy :utilizingiaflceyi sig- Nnal designating.v saidrspacedfftiniefiintervais-and received-.over aline circuitgsaid receiver=fcom prisingz reproducing imeans; circuits fineans' for .supplying said electricarsignalsfto SsaidreproducyingY means ydecoding"apparatus "included finisaid fcrcuitfmeans andrespons'ive toianlfappliedisignal 'for :decodingcsaid f electrical! signals ;-'.a separating Ycircuit coupled v'to' said circuit 1means Fior f'selecting I said *decoding f signal't and fiori suppl-ying'l said vde fcoding signal torsaid'ddecoding apparatuspiand =a`pparatus coupled ffto-saidf-line circuititand' disposed---between ysaid `fseparating'-.i circuitaiandisaid fdecodin'g rapparatus sand? .responsive ito. said-key Tsignal `for' altering during fsaid'; spacedfintervals --said characteris'tic"ofY :said- Vdecoclirlgesignahas applied to said decoding apparatus to compensate for -the alterationsinfsaid-echaracteristic A*ofisaid coding signal. 4 d

n2.. A subscriptiontelevision receiver `for--utiliz ingla television .signal vandamaudio signal atleast one ofwhich is codedin accordance-with acer- 'tan coding schedule determined byFV a. charac--y teristic of a codingv-sgnalfor vvhichsaid characteristic 'is altered during Vspaced timeeintervala auwior tilinga decodingsignal-havingsawharacteristc lcor-responding :to said characteristic said coding signal and receivedconcurrently with said television and audio nsignals, :La-nd'for :also utilizing a key signaldesignating said-vspaced-time .intervals and received over aline circuit, said receiver comprising: reproducing v-means.; --circnit -means for supplying ,said 4.tr-:leVis-ion iand'faudio signals to said reproducing'means; idecodingrap- -paratus included .ein lsaid circuit means :and :aresponsive .to 'ian applied-signal for :decodingmsaid coded `one .of said televisionfand raudioisgnais; .ita iilter' circuit coupledito said:circuittimeansiiorise 4lecting 'said decoding .signal fand :for supplying :said deco'dingsign'al .to :said: decoding iapparatus;

andapparatus coupled to .said slin'e :circuit 'disposedxbetween 'said-filter circuit and said fdccoding apparatus and responsive to key .signal for .altering V'during :said spaced-.intervals said characteristicpof. said:.decoding:signalsasfap- J plied .to V:said "decoding apparatus to .f'compensate .'for th'e. alterations in said .characteristicfofsaid .coding signal.

.3. A subscription televisioni-receiver 'for1i1tili-zingla' televisionsignal coded in accor'danceiwithea certain coding schedulefdetermined Iby ;a charac- 'teristicgof a .coding signal. for which saidcharacteristic is alteredduring spaced time-intervals, and for utilizing a decoding signalliavin'gfachap acteristicv corresponding itc'saidicharacteristicedf said coding .signal and r'eceivedf-ccncurreritlywith said televisionl signal, and for'alsofutilizingea'flrey signal' designating said vspaced" time iiri-tervallseaiiid received over a linecircuit, said receiver l"comprising reproducing means f .circuit meansfior'snp- .plyingi saidftelevision sig-nal ato saidvreprodumg means; decoding apparatusfincluded insaidfcir cuit means and 4responsive tol-an appliedesignl .for decoding said television sig-nal; -'afil-te1'-cir cuit coupled to said circuitmeansior @selecting said decoding gsignal' and''for supplying said; "decoding signal -to `saiddecodingapparatus land vimparatus'coupledfte 'fsaid 1li-riecircuits and vdisposed-between -rsaitl ffilter :circuit-,rand fsaid idecodling. apparatus anderesp'onsivef-ltoffsaidileey signal for v altering fidu'ring said yspaced l'iritervais vsciiti characteristic; of-flsaidf'decodinglsignalas applied 'to i said decodingapparaitusgto cmp'ensatefor'fthe -f-alteifations'linfsaid-fcharacteristic f'fasaiidffcoding isignal.

.-4.--1K:subscriptionf'television receiveriifor'utiliz- Av'ing altelevisionfsignalfcodd infaccordance-Withfa certainv coding schedule determined-by a charac- 'f'iteristic 1ofi-a coding:'sig-IialiiforI Whiclrsaidrcha'racteristic is altered `during spaced time intervals, and `for vutilizing an audio'ffsignalreceived conrcurrently with said .televisien--signal# aridcmcdulatedwith la ld'e'coiiing-'--`signal having ri-'characl-teristic flcorresponding Ltosaid-l characteristiciof said'codingrlsignalgarid for alsoutilicing zal-keyingnall designating --said dspacedl' time intervals *and received "overa-fa'. 'linelfcircuiowsai'd rreceiverl comprising :i 'an'v imageereproiucing-ideviee rfapparatus fforfsuppl-ying :sadltelevis'ion signalftosaid"repro 'ducing device; `adeccfding1 cireiiitdncluied in'esaid apparatus -andlresp'onsive4 to'fan'appiiedrsignlffor decr ding..said7 televisionsignal ;L assouiidwrepro- .fducingfi devlce appara-tus'ffor supplying 'said audio #signal tcl said soundLrepr-oducing device ;v' afin-Iter :circuit 'eoupl'edtofsaid a-udisignalfsupplying-ap- Sparatusifor y'separating saiddec'oding signaliirmn Isaid: audio signal and fforsupplyingfsai'd'idecoding s-ignal to said; decodingfappa-ratus :land-apparatus coupled y-tovsaid dine" circuitrand. disposedrhetween ssaid `iilter `circuit.: and .saidffrclecodingfrcircuitsand vresponsive-etcA saidifflceyiisignal :forcalterimg'idming said 'spaced intervals said characteristic of said decoding signal as applied to said decoding circuit to compensate for the alterations in said charac- `teristic of said coding signal.

5. A subscription television receiver for utilizing a television signal including video-frequency components and synchronizing-signal compo- -over a line circuit, said receiver comprising: an image-reproducing device and an associated scanning system; apparatus for supplying said television signal to said reproducing device and said scanning system; a decoding circuit included in said scanning system and responsive to an applied signal for changing a timing characteristic of said scanning system to compensate for said variations in the relative timing of said video and synchronizing components; a sound-reproducing device; apparatus for supplying said audio signal to said sound-reproducing device; a filter Acircuit coupled to said audio-signal supplying apparatus for separating said decoding signal from said audio signal and for supplying said decoding signal to said decoding circuit; and apparatus coupled to said line circuit and 'disposed between said filter circuit and said decoding circuit and responsive to said key signal for altering during said spaced intervals said characteristic of said decoding signal as applied to said decoding circuit to compensate for the alterations in said characteristic of said coding signal.

6. A subscription television system comprising: a picture-converting device and an assoiciated scanning system; a synchronizing-signal ;source coupled to said scanning system for supplying synchronizing pulses thereto to control :the timing of said device; a pulse phase modulator disposed between said synchronizing-signal source and said scanning system; and a signal source coupled to said modulator for supplying I a continuous wave signal thereto to vary the timing of said synchronizing pulses in accordance with the characteristics of said continuous wave signal.

7. A subscription television system comprising: a picture-converting device and an associated scanning system; a synchronizing-signal source coupled to said scanning system for developing synchronizing pulses to control the timing of said device; a pulse-phase modulator disposed between said synchronizing-signal source and said scanning system; and a signal source coupled to said modulator for supplying a sine-wave coding signal thereto to vary the timing of said ,synchronizing pulses in accordance with the characteristics of said sine-Wave signal.

8. A subscription television system comprising:

a picture-converting device and an associated scanning system; a synchronizing-signal source coupled to said scanning system for developing synchronizing pulses to control the ltiming of said device; a pulse-phase modulator disposed between said synchronizing-signal source and said scanning system; a signal source coupled 1.o said modulator for supplying a continuouswave signal thereto to'vary the timing of said synchronizing pulses in accordance with th'e characteristics of said continuous-Wave signal; and apparatus disposed between said signal source and said modulator for altering a characteristic of said continuous-wave signal at least during spaced intervals.

9. A subscription television system comprising: a picture-converting device and an associated scanning system; a synchronizing-signal source coupled to said scanning system for developing synchronizing pulses to control the timing' of said device; a pulse-phase modulator disposed between said synchronizing-signal source and said scanning system; a signal source coupled to said modulator for supplying a continuouswave signal thereto to vary the timing of said synchronizing pulses in accordance with the characteristics of said continuous-wave signal; and apparatus disposed between said signal source and said modulator for inverting the phase of said continuous-Wave signal during spaced intervals.

10. A subscription television system comprising: a picture-converting device and an associated scanning system; a synchronizing-signal source coupled to said scanning system for developing synchronizing pulses to control the timing of said device; a pulse-phase modulator disposed between said synchronizing-signal source and said scanning system; a signal source coupled to said modulator for supplying a continuous-Wave signal thereto to vary the timing of said synchronizing pulses in accordance with the characteristics of said continuous-Wave signal; apparatus disposed between said signal source and said modulator responsive -to an applied key signal for altering a characteristic of said continuous-wave signal; and a key-signal source coupled to said last-named apparatus for supplying said key signal to said apparatus during spaced intervals.

11. A subscription television system comprising: a picture-converting device and an associated scanning system; a synchronizing-signal source coupled to said scanning system for developing vertical and horizontal synchronizing pulses to control the timing of said device; a pulse-phase modulator disposed between said synchronizing-signal source and said scanning system; a signal source coupled to said modulator for supplying a sine-wave coding signal thereto to vary the timing of said horizontal synchronizmg pulses inl accordance with the characteristics of said sine-wave signal; a phase inverter disposed between said signal source and said modulator for inverting the phase of said coding signal in response to an applied signal; a circuit coupled to said synchronizing-signal source and to said phase inverter for applying a control signal to said phase inverter to actuate said phase inverter; and a key signal source coupled to said circuit for supplying a key signal thereto to condition said circuit during spaced intervals for actuation by said vertical synchronizing pulses.

1.2. A subscriber receiver for utilizing a television signal coded in accordance with a certain coding schedule comprising: an image-reproducing device; a circuit for receiving said telev'1s1on signal and for supplying said television signal to said reproducing device; decoding apparatus responsive to an applied signal for eiectively decoding said television signal; means for derlvmg a iirst decoding signal representing a first coding schedule; means for deriving a second decoding signal representing a second coding Schedule so related to said first coding schedule that operation of one of said decoding signals upon the other produces a third decoding signal representing said coding schedule of said television signal; apparatus coupled to said means to receive said first and second decoding signals and to produce said third decoding signal; and means for coupling said last-mentioned apparatus to said decoding apparatus effectively to decode said television signal.

13. A subscriber receiver for utilizing a television signal coded in accordance with a certain coding schedule comprising: an image-reproducing device; a circuit for receiving said television signal and for supplying said television signal to said reproducing device; decoding apparatus responsive to an applied signal for effectively decoding said television signal; means for deriving a first decoding signal representing a rst coding schedule; means for deriving a second decoding signal representing a second coding schedule specifically different from but so related to said first coding schedule that operation of one of said decoding signals upon the other produces a third decoding signal representing said coding schedule of said television signal; apparatus coupled to said means to receive said first and second decoding signals and to produce said third decoding signal; and means for coupling said last-mentioned apparatus to said decoding apparatus effectively to decode said television signal.

14. A subscriber receiver for utilizing a coded television signal representing picture intelligence in a series of scanning fields recurring at a selected rate, said receiver comprising: an imagereproducing device; a circuit for supplying said television signal to said reproducing device; decoding means for effectively decoding said television signal; a control system for supplying an actuating signal to said decoding means to actuate said decoding means at a rate faster than the aforesaid selected recurrence rate of said scanning fields; and means coupled to said control system for varying said actuating signal and the actuation of said decoding means at a rate slower than said selected recurrence rate of said scanning iields.

l5. A subscription television system comprising: means, including an image converter and an associated scanning system, for translating a television signal representing an image; a first encoding device coupled to said means for varying the operating mode thereof to effect encoding of said television signal; means for deriving a first encoding signal having a predetermined characteristic which varies in accordance with and represents a first coding schedule; a second encoding device coupled to said last-mentioned means to receive said first encoding signal and vary said characteristic thereof to derive a second encoding signal representing a second coding schedule; and means for supplying one of said encoding signals to said first-mentioned encoding device to actuate said device in accordance with the coding schedule represented by that signal.

16. A subscription television receiver for utilizing a coded television signal comprising: an image-reproducing device for producing the intelligence represented by said television signal; apparatus for receiving said television signal and for utilizing said signal to control said reproducl) ing device; a first decoding device coupled to said apparatus and responsive to an applied actuating signal for varying the operating mode of said apparatus effectively to decode said television signal; means for deriving a first decoding signal having a predetermined characteristic which varies in accordance with and represents a first coding schedule; a second decoding device interposed between said last-mentioned means and said first decoding device and responsive to an applied actuating signal for altering said characteristic of said first coding signal to develop a decoding signal and for effecting actuation of said first decoding device; a signal source for deriving a second decoding signal representing a second coding schedule; and means for supplying said second decoding signal to said second decoding device to effect actuation thereof in accordance with said second coding schedule.

17. A subscription television receiver for utilizing a coded television signal, including video and audio components, and a concurrently received decoding signal having a predetermined characteristic which varies in accordance with and represents a first coding schedule, said receiver comprising: an image-reproducing device for reproducing the intelligence represented by said television signal; apparatus for receiving said television signal and for utilizing said signal to control said reproducing device; a first decoding device coupled to said apparatus and responsive to an applied actuating signal for varying the operating mode of said apparatus effectively to decode said television signal; means for separating said decoding signal from said television signal; a second decoding device interposed between said last-mentioned means and said first decoding device and responsive to an applied actuating signal for altering said characteristic of said decoding signal to develop a modifled decoding signal for effecting actuation of said first decoding device; a signal source for deriving a second decoding signal representing a second coding schedule; and means for supplying said second decoding signal to said second decoding device to effect actuation thereof in accordance with said second coding schedule.

RICHARD O. GRAY. ERWIN M. ROSCHKE.

References Cited in the file of this patent UNITED STATES PATENTS Number FOREIGN PATENTS Country Date Great Britain Jan. 26, 1933 Number 

